This invention relates generally to electronic components and more particularly concerns low profile surface mountable sensing coils having a structure that improves the manufacturability and performance of the component.
The electronics industry provides a variety of wire wound components such as inductors which come in a variety of package types and configurations. For example, inductors may be provided in toroid, solenoidal, drum or sling-type packaging and in through-hole or surface mount configurations.
Of these coil components, some are used as sensors for detecting magnetic fields and rely on the use of highly permeable materials to detect the presence of such fields. For example, in U.S. Pat. No. 4,851,775, issued Jul. 25, 1989 to Kim et al., a digital compass and magnetometer are disclosed which use a solenoidal sensor coil having a wire-wound bobbin with an amorphous metal having a high magnetic permeability inserted therein for detecting magnetic fields. Improvements on these compass and magnetometer designs, as well as new applications for such sensor coils, are disclosed in U.S. Pat. No. 5,239,264, issued Aug. 24, 1993 to Hawks; U.S. Pat. No. 5,642,046, issued Jun. 24, 1997 to Hawks; U.S. Pat. No. 5,744,956, issued Apr. 28, 1998 to Hawks; U.S. Pat. No. 6,084,406, issued Jul. 4, 2000 to James et al.; and U.S. Pat. No. 6,243,660, issued Jun. 5, 2001. All of the above-mentioned patents are hereby incorporated herein by reference.
Although many advances have been made in the application of such sensor coils, most (if not all) of the available components continue to use a coil component configuration wherein the highly permeable amorphous metal layer is inserted into a plastic bobbin. The reason for this is that amorphous metals are extremely sharp and must therefore be prevented from rubbing against the wire windings. For example, if the wire winding is placed directly on the amorphous metal, the amorphous metal will eventually cut through the outer insulation of the wire and cause the component to short. In extreme cases, the amorphous metal may even cut the wire of the component causing the component to open (or operate as an open circuit).
To avoid such problems, the amorphous metal has traditionally been inserted into a plastic bobbin to isolate the amorphous metal from the wire winding. For example, in FIG. 1 of U.S. Pat. No. 6,084,406, a traditional sensor coil is disclosed in which plastic bobbin 13 isolates an elongated core of high dc permeability material 17 from electrically conductive wire 15. In another traditional coil sensor structure, a slot is provided in the bobbin for receiving the amorphous metal; however, in this configuration the amorphous metal is able to slide out of the slot and make contact with the wire winding hindering the use and marketability of this design.
Another example of a traditional coil sensor is illustrated in FIGS. 5A-F herein, and is identified generally by reference numeral 10. The coil sensor 10 includes a bobbin 12 having first and second bobbin portions 12a and 12b, respectively, which can be interconnected (e.g., snapped together) via a pair of post members 14a and post receiving recesses 14b. An amorphous metal 16 is sandwiched between the first and second bobbin portions 12a-b in order to isolate the amorphous metal 16 from the wire winding 18 which is wound about the interconnected bobbin 12.
One problem associated with the use of the above-mentioned sensor coil structures is the large gap that is created between the amorphous metal and the wire winding. More particularly, the gap created between the amorphous metal and the wire winding requires the winding to have many more turns in order to achieve the desired sensitivity for detecting magnetic fields. In other words, the larger the gap, the more turns the wire winding must have. Thus, the gap present in existing structures hinders the ability to make smaller and more efficient sensor coils with fewer number of turns.
Another problem associated with existing sensor coil structures is that it is difficult (if not impossible) to automate the assembly of such structures. More particularly, the necessity of inserting the amorphous metal into a bobbin to isolate it from the wire winding requires hand assembly of at least a portion of the component. This increases the amount of time and cost it takes to produce sensor coils and reduces the accuracy with which such components can be mass produced.
Accordingly, it has been determined that the need exists for an improved wire wound component and method for manufacturing the same which overcome the aforementioned limitations and which further provide capabilities, features and functions, not available in current devices and methods for manufacturing.